Tropical Storm KARINA

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TROPICAL STORM KARINA DISCUSSION NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014
200 AM PDT FRI AUG 15 2014
Karina continues to experience 20-25 kt of easterly vertical wind
shear, which has caused the center to become partly exposed on the
eastern side of the deep convection. Satellite intensity estimates
are 65 kt from SAB and 55 kt from TAFB. The initial intensity is
decreased to 60 kt, and this may a little generous.
The initial motion is now 275/10. Karina remains on the south side
of a mid-level ridge that extends from the southwestern United
States westward over the Pacific. This feature should steer the
storm generally westward to west-northwestward for the next 2-3
days. After that time, the guidance becomes divergent, partly due
to how the models show Karina interacting with other nearby tropical
disturbances. The ECMWF and Canadian models forecast a low pressure
area east of Karina causing the cyclone to turn generally west-
southwestward. The UKMET and NAVGEM also show a low to the east.
However, they forecast it to have less influence on Karina, with the
UKMET showing a continued westward track and the NAVGEM showing a
turn toward the north. The GFS shows less development east of
Karina and instead forecasts the cyclone to interact with a
disturbance to the southwest, which causes Karina to continue
westward to west-northwestward. Given the uncertainty, the new
forecast track will follow the previous forecast in showing a
west-southwestward turn in best agreement with the ECMWF, HWRF, and
the Florida State Superensemble models. The new track lies to the
south of the center of the guidance envelope and the other consensus
models.
The dynamical models suggest the current shear could continue for
another 24-30 hours. Based on this and the current structure of
the storm, the early part of the intensity forecast is revised
significantly downward from the previous advisory. After that time,
the forecast remains tricky. The shear is expected to decrease
while Karina moves over sea surface temperatures of near 26C. This
could allow Karina to re-intensify as forecast by the GFDL and the
Navy COAMPS models. However, any deviation north of the forecast
track would take the system over colder water, which would prevent
strengthening. The possible interaction with the other disturbances
would also hinder re-intensification, and the Canadian model shows
Karina starting to get absorbed by the eastern disturbance near the
end of the forecast period. Since there are so many possibilities,
the latter part of the intensity forecast is low confidence. It
calls for Karina to maintain a 50 kt intensity from 24-120 hours,
which is stronger than much of the guidance.
FORECAST POSITIONS AND MAX WINDS
INIT 15/0900Z 17.2N 119.1W 60 KT 70 MPH
12H 15/1800Z 17.6N 120.7W 55 KT 65 MPH
24H 16/0600Z 18.1N 122.9W 50 KT 60 MPH
36H 16/1800Z 18.4N 125.0W 50 KT 60 MPH
48H 17/0600Z 18.4N 127.0W 50 KT 60 MPH
72H 18/0600Z 18.0N 131.0W 50 KT 60 MPH
96H 19/0600Z 17.5N 134.0W 50 KT 60 MPH
120H 20/0600Z 17.0N 136.5W 50 KT 60 MPH
$$
Forecaster Beven
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